The island has an area of 51.5 km2 (19.9 sq mi). It is about 17.5 km (10.9 mi) from north to south and 5 km (3.1 mi) wide at its central part. It is generally low lying and has been used as a sheep farm for more than a hundred years.[2] It is separated from Lafonia by the Eagle Passage, which takes its name from Speedwell Island's old name. Speedwell Island is the largest of the Speedwell Island group, which includes the Elephant Cays, George Island, Barren Island and Annie Island.[2]

In 1812 the British ship Isabella, captained by George Higton, was shipwrecked off "Eagle Island" (as it was then) Most of the crew were rescued by the AmericansealerNanina, commanded by Captain Charles Barnard. However, realising that they would require more provisions for the expanded number of passengers, Barnard and a few others went out in a party to retrieve more food. During his absence the Nanina was taken over by the British crew and left them on the island. Barnard and his party were finally rescued in November 1814. In 1829 Barnard wrote A Narrative of the Sufferings and Adventures of Capt. Charles Barnard detailing the happenings.

The 1837 survey of the Falkland Islands under Lowcay noted that there were wild pigs on the island.

In 1929, Alexander Dugas, a Frenchman employed on Sealion Island committed suicide and his companions felt it necessary to inform the authorities. But the lack of harbors meant that no boat of any size could be kept on the island and so a determined individual called Benny Davis constructed a makeshift craft from wooden barrels and launched it into the surf. The remarkable sailor set out just before dark, and arrived at Speedwell Island some twelve hours later. He explained that he had simply headed west and then taken his direction from the smell of the cormorants on Annie Island.[3]